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Introduction to Antimicrobial Drugs: Classification, Cell Wall Synthesis Inhibitors, etc, Lecture notes of Pharmacology

This comprehensive Notes covers the introduction to antimicrobial drugs, their classification, and detailed explanations of drugs that inhibit cell wall synthesis and protein synthesis. Learn about macrolides and their role in treating infections, along with essential insights into various antimicrobial agents. Perfect for students and professionals looking to deepen their understanding of pharmacology and microbiology.

Typology: Lecture notes

2024/2025

Available from 12/13/2024

Dr_Raihan
Dr_Raihan 🇮🇳

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Introduction to Antimicrobial Drugs
Antibiotics
:
Substances
produced
by
microorganisms
.
which
suppress
the
growth
of
or
kill
other
microorganisms
at
very
low
conct
.
Drug
Resistance
:
Can
be
Natural
or
Acquired
.
Acquired
Resistance
may
be
due
to
-
(a)
Single
step
mutation
(
seen
with
Rifampicin
&
streptomycin
)
(b)
Multistep
mutation
(
seen
with
Erythromycin
,
tetracycline
)
Drug
Resistance
can
be
transferred
from
one
micro
-
-
organism
to
other
by
gene
transfer
.
-
Conjugation
-
Transduction
l
Transformation
.
Mechanism
of
Drug
Resistance
:
Four
main
mechanisms
:
iii
Drug
inactivation
or
modification
iiii
Alteration
of
Targ e t
site
ciiii
Alteration
of
Metabolic
pathway
in
Reduced
drug
accumulation
.
pf3
pf4
pf5
pf8
pf9
pfa
pfd
pfe
pff
pf12
pf13
pf14
pf15
pf16
pf17
pf18
pf19
pf1a
pf1b
pf1c
pf1d
pf1e
pf1f
pf20

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Introduction to Antimicrobial Drugs

Antibiotics :^ Substances^ produced by

microorganisms

. which

suppress

the growth of or kill other microorganisms at very low conct. Drug Resistance :

  • Can be (^) Natural (^) or

Acquired

.

  • Acquired Resistance may

be due to -

(a) Single step^ mutation (^) ( seen^ with^

Rifampicin

&

(b) streptomycin^ )

Multistep

mutation ( seen with Erythromycin ,^ tetracycline^ )

  • Drug Resistance (^) can be transferred (^) from one micro^ -

organism

to other by (^) gene transfer^ .

  • Conjugation
  • (^) Transduction l Transformation . Mechanism

of

Drug

Resistance :

  • (^) Four (^) main mechanisms (^) : iii Drug inactivation (^) or modification

iiii Alteration^ of

Target

site

ciiii Alteration of Metabolic pathway in (^) Reduced drug accumulation.

MedNotes [ www.mednotes.in ] Full MedNotes : mednotesebooks.company.site App Available on PlayStore ( iiis^ Bactericidal^ drugs are^ used^ in^ immunocompromised patients , not^ bacteriostatic in some^ drugs

are contraindicated^ in^ Renal^ disease^.

  • Cephalothin
    • Cephaloridine -^ Nitro^ furantoin
  • Mali dixie (^) acid

Tetracyclines

( except

doxycycline

( vs Drugs contraindicated in^ liver^ disease^.

  • Erythromycin estate

Tetracyclines

Pyrazinamide

  • Pefloxacin . ( vis^ Genetic Factors^ :^ Antimicrobial^ producing hemolysis in (^) G- GPD deficient (^) patients are^ :

Primaquine

Nitrofurantoin

Chloroquine

  • Dapsone
  • Quinine - Sulfonamides. C

Classification of Antimicrobial Agents

  • Antimicrobials (^) can be classified

a/c to^ several^

ways : TA ] Mechanism^ of Action^ : ii. Drug inhibiting^ cell wall^ synthesis :

iii. Drugs inhibit^ Protein^

synthesis : ciiis Drugs (^) causing leakage^ from^ cell Membrane^ : car Polypeptide Antibiotics (^) : Polymixin B.^

Cole 's tin^.

and tyrothricin

(c) Arabinogalactan (^) synthesis inhibitors (^) : Ethambutol

[ B. ] Based (^) on Type of Action^ : ( is^ Bacteriostatic^ ( (^) stop the growth of bacteria (^) ) in (^) Bactericidal (^) ( kills bacteria ) (c) Based on spectrum (^) of (^) Activity : ( is^ Narrow^ Spectrum -^ Penicillin^ G

, streptomycin^ ,

Erythromycin

in Broad

spectrum

Tetracyclines , chloramphenicol.

Drugs Inhibiting Cell Wall Synthesis - 1

  • All^ cell (^) wall synthesis

inhibitors are Bactericidal.

  • They are divided into (^) B- lactams &^ non - B lactam drugs.
  • P lactam^ antibiotics^ are^ those^ drugs that^ contain

P

  • (^) lactam

ring ,

include : (a) Penicillins (b)

Cephalosporins

(c) Monobactams (d) (^) Carbapenems.

Penicillins

  • Mechanism of Action -^ Penicillins^ interact^ with cytoplasmic membrane (^) - binding proteins^ ( PBR^ )^ to inhibit (^) transpeplidation reactions^ involved in crosslinking,^ the^ final step in Cell^ -^ wall^ synthesis .
  • (^) Mechanism

of

Resistance :

(a) Penicillin^ ases (^) ( B^ -^ lactamases^ ) break lactam^ ring .

( As^ in

staphylococci

(b) structural changes in PBPS^ of Bacteria^. ( (^) As :^ methicillin -^ resistant

staphylococcus

aureus [ (^) MRSA] , (^) penicillin -^ resistant^ pneumococci.^ ) (c) Changes

in Porin^ structure. ( As^ :^ Pseudomonas )

  • Overcoming

Resistances /

shortcomings :

(a) Activity

of

Penicillin enhanced if used in combination with P

  • (^) lactamase inhibitors. ( clavulanic^ acid^ ,^ sulbactam^ )
  • Penicillin^ ✗

(b) Acid Resistant Penicillins :

0 - (^) Oxacillin D- Dicloxacillin [VODKA^ ] K -^ Cloxacillin

A- Amoxicillin

MedNotes [ www.mednotes.in ] Full MedNotes : mednotesebooks.company.site App Available on PlayStore

-^ N^ afcillin and^ Oxacillin^ eliminated^ largely in Bile.

  • Ampicillin (^) undergoes Enterobepalic (^) cycling , but excreted

by kidney

.

  • Benz (^) a theme penicillin G^ - (^) with (^) 1-1/2--2 weeks (^).
  • Side^ effects : (a) Hypersensitivity ( in^ 5-7% He From Urticaria^ skin^ Rash to

Anaphylaxis are^ possible

. (b) GI^ distress^ , (^) esp. Ampicillin

(c) Janisch^ -^ Her^ ✗^ heimer^ Reaction

in treatment^

of syphilis .

  • Clinical Uses^ : C

Drugs Inhibiting Cell Wall Synthesis - 2 Cephalosporins

  • Semi synthetic antibodies (^) derived from cephalosporin^ - (^) C (^).
  • Chemically related to

penicillin

.

  • These are

p

  • lactam antibiotics having dihydro^ thiazine ring

( 7-^ amino

cephalosporin

anic acid (^) ).

  • (^) All cephalosporins are Bactericidal^.
  • Classified into^4 generations :

-^ Most^ enter^ CMS^ :^ important in^ empiric management of^ Meningitis & Sepsis . 1- D^ ]^ Fourth^ Generation :

  • Hider^ spectrum
  • Resistant to most (^) B- lactamases
  • Can enter CMS.

Imipenem & Meropenem

  • (^) Side

effects :

la > Hypersensitivity

  • (^) Incidence 2%
  • Rashes &

Drug

Fever

  • Positive^ coomb 's Test , but rarely (^) hemolysis
  • There is 100% complete Cross reactivity between different (^) cephalosporins & (^) also (^) 5- 10% cross - reactivity with Penicillins.

Ceftazidime is^ implicated

in causing Neutropenia . Carbapenems

  • Mechanism of Action^ :
  • Same (^) as penicillins and^ cephalosporins

Resistant to p

  • lactamases (^).

Spectrum :

  • Gram + (^) ve cocci , gram -^ ve^ rods^ &^ anaerobes^.

Important

in - hospital (^) agents for^ empiric use in severe (^) life - threatening infections^ .

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App Available on PlayStore

c

Drugs Inhibiting Protein Synthesis - 1

  • According to spectrum (^) of Activity. these may be classified as : (a) (^) Broad

Spectrum

:

Chloramphenicol

& Tetracycline (b) Moderate^ Spectrum

: Macrolides & keto tides

(c) Narrow^ spectrum : Lin (^) cos amides (^) , streptogramins and Oxazolidinones^. Mechanism & Site I